A rapidly increasing number of hormones and bioactive peptides are becoming available to medical researchers. These drugs cannot be orally administered, so it is important to investigate their pharmacological effects as depot injections, first in animals and eventually in humans. The cost of peptide drugs is so high, however, that research programs of SBIR scope can afford to prepare experimental injectable formulations only on a very small scale. BIOTEK therefore proposed to develop a small scale preparative method for peptide-containing microcapsules based on harmless, biodegradable polylactide-co-glycolide (PLG) materials; past studies have shown that most peptides remain bioactive after being loaded into PLGs, stored, and released in vivo. The approach relies on a method developed by BIOTEK for other delivery systems: spray coating an aqueous solution of the peptide onto pure polymer microspheres and then overcoating with biodegradable polymer solution. Relatively inexpensive LHRH will be used as a model peptide. A 1-4 week release will be achieved using in vitro methods, and in vivo rat studies will confirm released bioactivity. Phase II will seek to make this technology available to NIH for custom preparation of experimental microcapsules and will apply it to a peptide of sufficient medical and commercial interest to encourage private sector support of Phase III commercialization.